The present invention is concerned with automatic slicing machines, and more particularly is directed to a novel method and system for automatically controlling slices cut by a machine so as to produce a group of slices within defined thickness variation limits and in a manner which improves the overall quality of the group of slices, as well as reduces product give-away and lowers waste.
In the slicing of food products, for example the slicing of pork bellies into bacon strips, the slicing operation is carried out in a cyclic fashion. During each cycle a desired number of slices, forming a group known as a draft, are sliced from the pork belly. After one draft is sliced the slicing operation is momentarily interrupted while this draft is carried away from the slicing blade, for example by a conveyor belt, and then the slicing of the next draft begins.
The production of a draft of the sliced product is controlled primarily on the basis of the weight of the product in the draft. For example, bacon is often sold in one pound packages. According to various regulations that protect consumer interests, a package of food that is sold according to weight must contain an amount of the food product that weighs at least the amount specified on the package. While it can contain more than the specified weight, from the producer's point of view it is desirable to maintain the amount of food product in the package as close to the specified weight as possible, without going under it. Including excess amounts of the food product, often referred to as "give-away," can result in significant losses when the producer sells a large volume of the product.
Accordingly, various systems have been devised to automatically control the slicing of a food product so that the actual weight of the draft is as close as practicable to its nominal, i.e. listed, weight. In the past, such control may have been carried out by weighing a draft after all of its slices had been cut, and adjusting the slicing machine so that the slices in subsequent drafts were thinner or thicker if the measured draft was over or under weight, respectively. Such an operation might be labelled a "static" one, since the slicing operation with respect to a draft was completed before that draft's weight was measured.
While better than totally manual systems, these static systems nevertheless had certain limitations. In particular, in these types of systems the correction factor that was applied to subsequently cut slices represented an average weight per slice for the number of slices in the measured draft. This averaging of error over the entire draft does not provide the best results, since a pork belly will vary in weight, height and composition, i.e. ratio of fat to lean, along its length. Thus, the first slice in a draft often may not weigh the same as the last slice in that draft or the slices in the next draft, even if all slices have the same thickness.
This problem is further exacerbated in the high-speed slicing machines that are prevalent in today's industry. Because of the high rate of speed at which these machines slice the product, accurate information about the weight of a draft may not be available until slicing of the third or fourth draft subsequent to the measured draft. Accordingly, if the composition or size of the pork belly varies for each slice, the discrepancy between the average weight per slice of the measured draft and the actual weight per slice of the draft presently being produced could be significant.
As a result, more modern control systems have employed a dynamic control mechanism in which the weight of the draft is determined as the slices are being cut, rather than after the draft is completed. For example, the systems disclosed in U.S. Pat. Nos. 3,508,591 and 3,995,517 weigh the partial draft as each slice is added. On the basis of the measured weight, a prediction of the final weight of the draft is made and used to control the thickness of further slices by varying the feed rate of the product to the slicer. Similarly, U.S. Pat. No. 3,906,823 discloses the process of weighing partial drafts of the product and using the partial draft weights to control the rate of feed of product into the slicer. Another example of a dynamic slice thickness control system is disclosed in commonly assigned, copending application Ser. No. 716,089.
Another factor which influences the sale price of the packages is the quality of the slices. During production, if the final weight of a package needs to be manually adjusted, the operator typically adds or substitutes other slices, e.g., partial or thin slices, that enable the desired final weight to be incrementally approached. These added slices may be less acceptable to the consumer, e.g. they may not cook at the same rate as the other slices, and the overall quality of the package is consequently reduced. When a draft contains slivers, wedge shaped or otherwise non-uniform slices, it will be downgraded and sold for a lower price. Thus, in the control of product slicing it is desirable to produce a draft of the target weight which contains only slices of uniform thickness, as well as to reduce waste in the form of end pieces and slivers, and thereby increase the overall yield per pork belly.
The manner in which the present invention achieves these objectives is explained hereinafter with reference to a preferred embodiment illustrated in the accompanying drawing.